The UK's most complete GLP-1 guide
Every Question Answered. Every Side Effect Explained.
- How GLP-1 medications work
- Mounjaro vs Wegovy compared
- Injection instructions
- Side effects & solutions
- What to eat on treatment
- FAQs answered
Free tracker included with every download this week
Why Has Your Weight Loss Slowed On Mounjaro?
If your weight loss has slowed or stopped while taking Mounjaro, you're not alone — weight loss plateaus are a normal part of any weight management journey. Weight loss doesn't progress at the same rate throughout your treatment. Understanding why this happens and what options are available can help you decide what to discuss with your prescriber. This guide explains the common reasons for slower weight loss on Mounjaro and what steps might help.
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Calculate Your BMI Instantly
Enter your height and weight below. Supports both imperial (stone & lbs) and metric (kg). Results include NHS category, healthy weight range, and ethnicity adjustments.
What Is BMI and Why Does It Matter?
Body Mass Index (BMI) is the most widely used screening tool for assessing whether your weight falls within a healthy range. Used by the NHS, GPs, and weight management services across the UK, BMI provides a quick snapshot of your weight relative to your height. The formula is simple: your weight in kilograms divided by your height in metres squared (kg/m²).
While BMI isn't a perfect measure — it doesn't account for muscle mass, bone density, or fat distribution — it remains the standard first step in identifying potential weight-related health risks including type 2 diabetes, cardiovascular disease, high blood pressure, and certain cancers.
The NHS also recommends adjusted thresholds for people of South Asian, Chinese, or Black African heritage — a BMI of 23 or above is classified as overweight, and 27.5 as obese. Our calculator includes this adjustment as a one-click toggle.
Why Weight Loss Slows On Mounjaro
Weight loss typically follows a pattern rather than a straight line downward. When you first start Mounjaro, your body responds to the appetite-suppressing effects of the GIP and GLP-1 receptor agonist mechanism, which may result in more rapid initial weight loss. Over time, several factors can cause weight loss to slow:
- Your body adapts: As weight decreases, your body requires fewer calories to maintain itself. This means the same calorie deficit that produced 2kg loss per week initially may only produce 0.5kg loss per week later.
- Medication plateau: The appetite-suppressing effects of Mounjaro may reduce slightly over time as your body becomes accustomed to the dose.
- Lifestyle changes: If diet or activity levels shift, weight loss can slow even on medication.
- You're approaching your natural weight: Mounjaro works best when used alongside reduced-calorie diet and physical activity — if either of these changes, progress may slow.
This is physiologically normal and does not mean Mounjaro has stopped working.
Clinically BackedWeight Loss
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How It Works
Three simple steps to understand your weight and take action.
Enter your height and weight in our free calculator. Get your BMI, NHS category, healthy weight range, and ethnicity-adjusted thresholds instantly.
If your BMI suggests you're overweight or obese, explore our GLP-1 calculators to project potential weight loss on Mounjaro or Wegovy.
Use our progress tracker to log your weight weekly, visualise your journey with charts, and stay motivated — all stored privately in your browser.
Free Weight Loss Tools & Guides
Everything you need to understand your weight, explore medication options, and track your progress — completely free.
What You Can Discuss With Your Prescriber
If your weight loss has genuinely plateaued, your prescriber may consider several options. A dose increase is common — if you're still on a maintenance dose below 15mg, your prescriber may suggest stepping up to the next dose level. You'll typically stay on each new dose for at least 4 weeks before assessing progress. Your prescriber may also review your diet and activity levels, as sustained weight loss requires ongoing calorie deficit alongside medication. Some people find that structured dietary support, increased physical activity, or both can help restart progress. You might also use our GLP-1 weight loss calculator to review realistic projections at your current dose versus a higher dose.
- Dual GIP/GLP-1 receptor agonist
- Up to 22.5% body weight loss (SURMOUNT-1)
- Weekly injection, dose escalation over 20+ weeks
- Available via private prescription in the UK
- Doses: 2.5mg → 5mg → 7.5mg → 10mg → 12.5mg → 15mg
- GLP-1 receptor agonist
- Up to 15–17% body weight loss (STEP trials)
- Weekly injection, 5-step dose escalation
- NHS & private prescription available
- Doses: 0.25mg → 0.5mg → 1mg → 1.7mg → 2.4mg
Mounjaro vs Wegovy: Head-to-Head
A side-by-side comparison of the two most popular GLP-1 weight loss medications available in the UK.
| Feature | Mounjaro | Wegovy |
|---|---|---|
| Drug class | Dual GIP/GLP-1 agonist | GLP-1 agonist |
| Active ingredient | Tirzepatide | Semaglutide |
| Avg. weight loss | 15–22.5% | 12–17% |
| Key trial | SURMOUNT-1 (2022) | STEP 1 (2021) |
| Max dose | 15 mg weekly | 2.4 mg weekly |
| Escalation period | 20–32 weeks | 16–20 weeks |
| Administration | Weekly injection (pen) | Weekly injection (pen) |
| NHS availability | Private prescription only | NHS & private |
| Approx. private cost | £150–£250/month | £150–£300/month |
| Common side effects | Nausea, diarrhoea, constipation | Nausea, vomiting, diarrhoea |
Data sourced from SURMOUNT-1 and STEP 1 clinical trials. Costs are approximate and vary by provider. Always consult a prescriber.
Am I Eligible for Weight Loss Medication?
In the UK, eligibility for GLP-1 weight loss medications like Mounjaro and Wegovy is based on your BMI and overall health profile.
- BMI of 30 or above (obese)
- Age 18 or over
- No contraindicated conditions
- Committed to lifestyle changes
- BMI of 27 or above
- Plus type 2 diabetes
- Or high blood pressure
- Or obstructive sleep apnoea
Use our BMI calculator to check whether your BMI falls within the eligible range.
How We Built These Tools
Every calculator and guide on myweightcheck is built with accuracy and transparency in mind. Our BMI calculator uses the standard WHO formula with NHS-aligned category thresholds. Our GLP-1 projections are modelled on published clinical trial data from SURMOUNT and STEP studies.
All data stays on your device. We don't require sign-ups, and we don't store your health information on any server. Your progress tracker saves data locally in your browser using localStorage, so only you can see it.
We're based in the UK and our tools are designed specifically for UK users — supporting stone & lbs by default, referencing NHS guidelines, using NICE-approved medication data, and linking to GPhC-registered pharmacies.
Frequently Asked Questions
Common questions about BMI, weight loss medications, and our free UK tools.
Is it normal for weight loss to slow down on Mounjaro?
Yes, completely normal. Initial gradual weight management typically slows as your body adapts to lower weight and reduced calorie intake. This is expected on any weight loss medication and does not mean Mounjaro has stopped working.
Should I increase my Mounjaro dose if weight loss has slowed?
Only your prescriber should decide this. Dose increases on Mounjaro happen every 4 weeks and go up to a maximum of 15mg weekly. If you're below the maximum dose, your prescriber may suggest an increase — but this requires their clinical assessment.
Can I speed up weight loss by skipping meals or eating very little?
No — this is counterproductive and risky. Mounjaro works alongside a healthy reduced-calorie diet and physical activity. Extreme restriction can cause muscle loss, nutritional deficiency, and often backfires. Your GP or prescriber can advise safe, sustainable dietary approaches.
How long should I wait before contacting my prescriber about slowed weight loss?
If weight loss has plateaued for 4 or more weeks with no change, it's worth discussing with your prescriber. However, minor fluctuations week-to-week are normal — weight naturally varies daily. Track progress over weeks or months, not daily.
Is slowed weight loss on Mounjaro different from slowed weight loss on Wegovy?
The underlying reasons are similar — both are GLP-1-based medications with dose titration schedules. Mounjaro is a dual GIP and GLP-1 agonist, while Wegovy is GLP-1-only. Both follow similar weight loss patterns: rapid initial loss, then gradual slowdown as metabolism adapts.
Ready to take control of your weight loss journey?
Start with a free BMI check, explore your GLP-1 options, or begin tracking your progress today. No sign-up. No cost. Just results.